Resilient, high temperature resistant multiple conductor seal for conical ports



March 16, 1965 T. BOOP RESILIENT, HIGH TEMPERATURE RESISTANT MULTIPLE CONDUCTOR SEAL FOR CONICAL PORTS 2 Sheets-Sheet l 75 H u/w,

6 an e 7 5 0 0,0

INVENTOR.

BY mm ATTO/F/VA'V Filed Nov. 16, 1962 March 16, 1965 G. T. BOOP 3,173,992

RESILIENT, HIGH TEMPERATURE RESISTANT MULTIPLE CONDUCTOR SEAL FOR CONICAL PORTS 2 Sheets-Sheet 2 Filed Nov. 16, 1962 Gene 7 500 0 INVENTOR.

United States Patent Texas Filed Nov. 16, 1962, Ser. No. 238,303 3 Claims. ((31. 174-151) This invention pertains to seals, and more particularly to a seal between electrical conductors and a wall through which they pass. The invention makes practicable the sealing off of each charge unit of multicharge perforating guns, such as are used in perforating well pipes, and wherein the charges are separately fired by electrical blasting caps each connected by a separate wire to a selector switch supplying electric power, whereby the charges can be selectively fired. The charges may be those of a bullet type gun, e.g. as shown in US. Patent Number 2,636,561, or in a jet gun employing shaped charges, e.g. as shown in US. Patent Number 2,916,991.

According to a preferred embodiment of the invention, the Wire from each electric blasting cap is made of an electrically conducting material, eg copper coated with a strongly adhering thin sheath of insulating material, such as Teflon (tetrafluoroethylene). Each insulated wire is processed, e.g. by dipping in a bath of etching or adherent material to roughen its insulation. A plurality of roughened, insulated wires are molded in place in a resilient, non-conductive, conically tapered plug having a low elastic modulus, high compressive and, shear strength, and a seizing taper. The plug is inserted in a seat provided by a correlative conically tapered counterbore forming a shoulder around a passage through the wall separating adjacent charges in the perforating gun. An O-ring between theplug and seatprovides a seal at low pressure, the plug being held in the seat to pressurize the O-ring by means of a centrally apertured jam nut screwed into a threaded portion at the-mouth of the counterbore. It is intended that the charge on the side of the wall that receives the plug be exploded first, whereby the force of the explosion tends to drive the plug farther into its seat causing it to seal tighter the greater the force to be sealed against. The charge below the Wall will usually be the one fired first so that taper of the plug and seat flare out downwardly.

For a detailed description of a preferred embodiment of the invention, reference will now be made to the accompanying drawings wherein:

FIGURE 1 is an elevation showing the lower portion of a jet perforating gun;

FIGURE 2 is a vertical section through one of the connectors between the charge carriers of the gun shown in FIGURE 1;

FIGURE 3 is a vertical section through one of the charge carriers showing the charge assembly therein; and

though the invention is also applicable to expendable guns utilizing carriers and other parts made of readily frangible material.

The gun head 14 maybe a simple connection between the multiple wires from the several blastingcaps of the gun and a multiple-conductor cable going from the gun to the surface of the earth and thence to a multi contact 3,173,992 Patented Mar. 16, 1965 selector switch whereby electric power can be applied to any desired one of the wires to fire the associated charge. Alternatively the gun head 14 may be a unit incorporating a selector switch operated by remote control from the surface, whereby only a single conductor cable need be used to extend from the gun to the earths surface.

Referring to FIGURE 3, each charge carrier 11 is a cylindrical tube internally taper threaded at each end forming upper and lower boxes 20, 21. The boxes receive the tapered, threaded pins 23, 24 at the upper and lower ends respectively of the adjacent connectors 12.

A housing 30, containing a shaped charge, has its back end 31 received in a socket 32 in the wall of the carrier 11. The forward end of the charge is supported by seal thimble 33 disposed in an aperture 34 in the wall of carrier 11. The thimble 33 rests against shoulder 35 and is sealed in the carrier by gasket 36. A length 37 of prirna cord passes through a hole in the rear end 31 of the charge housing, to explode the charge when the prima cord is ignited. l s

A lower part 38 of the prima cord length 37fis' molded into a plastic block 40, adjacent an electric blasting cap 41. The block 40 has a plurality of spring contacts 42 disposed around its periphery, electrically engaging the Wall of the charge carrier 11 and also connected electrically by wire 43 to electric blasting cap 41.

A second wire 44 from the cap 41 is connected at 45 to a wire 46 which joins two other wires 47, 48 from two caps in the charge carriers below, and with them extends up between block 40 and the Wall of carrier 11, on past charge housing 30, to pinconnectors 50, 51, 52. The pin connectors 5952 are received in sockets 53,54,

'55 at the lower ends of wires 56, 57, 58. All the wires heretofore mentioned are insulated, except wire 43 going to the contacts 42 need not be insulated. Y

The insulated wires 56 -58 are molded in-plug 60. Other wires 61, 62, 63, are shown as also molded in the plug, but cut oil. at the ends of the plug-and not used. In case of a charge carrier at a higher level than the one illustrated one or more additional wires in the plug would be used instead of being cut off. In the case of charge carriers below the one illustrated, fewer wireswould be needed and more would be cut olf. The plug is manufactured with multiple wires so as to be useable at any level in the gun.

The wires molded into plug 60 are preferably copper wires of about .020 inch diameter (American Wire Gage #24), insulated by an adhering sheath .011 inch thick of Teflon (polytetrafiuoroethylene) continuously extruded thereon, providing a 1500 megohm resistance. Although a Teflon coating is suitable, other plastic materials of equivalent properties as to mechanical strength and electrical resistance could be used. I Y I In order to interlock the insulated wire with plug 60, the surface of the insulation is roughened. This is illustrated in FIGURE 4 wherein there is shown :a copper Wire 1550 with an insulation sheath 181 Whose surface is rough. The roughening of'the sheath can be'achieved either by etching, i.e. forming crevices inthe surface of the insulation, or by spattering with an adhesive material, or by mechanical action, e.g. knurling, or any other desired method or combination of methods. The insulation as initially formed on the wire could be originally produced to have the desired roughness if desired. A roughness of at least about 50 R.M.S. microinches should be employed. A roughness of R.M.S. microinches would be about as high as one would need to go, although there would be no objection to a roughness of 1000 R.M.S. microinches. Beyond that, the roughness might impair the effectiveness of the insulation. Q

The rough surfaced insulated wires such as 56, 57,

3. 58, 61, 62, 63 are molded in place in plug 60. The plug is made of a resilient, preferably non-conducting material, e.g. a synthetic resin, which is either thermosetting or has a high heat resistance if thermoplastic, and which either in the natural state or when compounded with a filler such as fibers of glass, has a high compressive strength and shear strength A suitable material could have the following properties? Flexural modulus of elasticity (5.92) (10 psi. Tensile strength 8500 psi. Compressive strength 23,000 psi.- Dielectric constantat 60 c.p.s. 2.93

Spec. gravity 1.11

Some types of methyl methacrylate and other polyesters meet these specifications. Polylvinylbutyral is another material that may be used. Phenolic plastic is a suitable material of the thermosetting type. Reichold Chemical Corp. formula HU-l65 is suitable.

The plug 60 has a taper of about A; inch in diameter per inch of length. This is a seizing taper. The plug is disposed in a seat provided by a correlatively tapered counterbore 65 at the lower end of connector 12 and by a shoulder 66 between counterbore 65 and passage 67 through the remainder of the connector. A rubber O- rlng 68 disposed in a groove 69 in counterbore 65 proyidesa low pressure seal therebetween. The o-ring may be made of natural or synthetic rubber, preferably oil and water resistant. The plug 60 is held against its seat under pressure by a centrally apertured jam nut 70 screwed into the threaded mouth 71 of the counterbore.

The wires 56, 57, 58 extend down from the plug 60 through central aperture 72 in the jam nut, and extend upwardly through passage 6'7 and the connector 12 to the charge carrier thereabove.

FIGURE 2 shows the connector 12 that would be next above the upper connector 12 of FIGURE 3. Thus, from socket connectors 75, 76, 77, 78, there are four wires 80, 81,- 82, 83 extending through the plug 60, and only'two wires 84, 85 cut off short. After passing through the connector 12 and into the charge carrier 11 thereabove' (not shown) the wires 80-83 are joined by a wire 86 from the blasting cap in that charge carrier and the five wires continue up to pin connectors 87, 88, 89, 90, 91'for connection to the lower ends of the wires from the plug 60' next above.

The wires going through the plug 60 are parallel to each other and preferably disposed in a regular symmetrical pattern, such as at the apices of adjacent equilateral triangles, with a minimum distance between wires preferably at least somewhat greater than the diameter of the wire, e.g. .050 inch, or a spacing pattern of A inch between centers.

The apparatus above described is intended to provide a seal between the insulated wires and the connector which will withstand pressures of 20,000 p.s.i. and higher. The bond between the wire insulation and the plug is sufficient to withstand higher pressures and it is only necessary to choose a material for the plug having the requisite compressive'and shear strength in order to seal at the higher pressures, for due to the tapered shape of the plug it seals more tightly as the pressure below increases, such pressure being due to the blast of the charge therebelow followed by the admission of the well fluid through the charge carrier wall and the resulting hydrostatic pressure. The construction according to the invention thus provides a seal that is satisfactory for all pressures that would normally be expected in the perforating gun service. The constructionis adapted to provide a multiconductor seal whose overall diameter is small enough to allow use in the smallest diameter guns, e.g. a gun of 1 /4 inch 'O.D. suitable for nominal 2% inch O.D. pipe whose ID. is about 1.9 inches.

While a preferred embodiment of the invention has been shown and described, many modifications thereof can be made by one skilled in the art without departing from the spirit of the invention, and it is desired to protect by Letters Patent all forms of the invention following within the scope of the following claims.

I claim:

1. A seal comprising a double pin connector having an externally threaded pin at each end thereof and having a passage extending therethrough from one pin to the other and having a counterbore at one end of the passage which together with a shoulder formed between the inner end of the counterbore and the adjacent end of the passage provides a seat,

said counterbore being conically tapered with a seizing taper flaring outwardly progressing away from said shoulder,

an annular groove around said counterbore having an O-ring seal therein,

a threaded mouth at the end of the counterbore farthest from said shoulder,

a resilient, high temperature resistant, non-electrically conductive plug conically tapered correlative to said counterbore disposed in said seat in engagement with said shoulder,

said plug being made of a thermosetting polyester synthetic resin having a compressive strength in excess of 20,000 psi. and a tensile strength in excess of 5,000 psi. and a flexural modulus of elasticity of the order of (6) (10 p.s.i.,

and a plurality of insulated electric wires disposed in said plug,

said wires being made of copper and insulated with a sheath of continuous polytetrafluoroethylene adhered thereto having a thickness of between .010 and .020 inch,

said sheath having a surface roughness of at least 50 microinches R.M.S.,

said wires being disposed with their lengths parallel to each other and the axis of the plug,

said wires being disposed in a uniform symmetrical spacing pattern, namely, at the apices of adjacent equilateral triangles with a minimum separation between the outer peripheries of the sheaths at least equal to the outer diameter of the sheath,

and a centrally apertured jam nut screwed into said mouth of the counterbore compressing said plug against said seat.

2. A seal comprising a tubular body having connection means at each end,

one end of the body having a conical counterbore with an outwardly flaring seizing taper and an annular outwardly facing shoulder around the counterbore spaced inwardly from said one end,

a resilient, high temperature resistant non-electrically conductive, plastic plug conically tapered correlative to said counterbore disposed in said counterbore in engagement therewith and with said shoulder,

a plurality of plastic insulated copper wires embedded in said plug extending therethrough parallel to the axis of the plug and each spaced laterally from the others,

the insulation on said wires being roughened on the surface where the wires pass through the plug,

said plug being molded with said wires in place forming an intimate bond between the plug and the insulation of the wires.

3. A resilient, high temperature resistant, non-electrically conductive plug,

the exterior of said plug being conically tapered with a seizing taper and adapted to seal in and seal with a correlatively tapered seat in a counterbore at one end of a passage through a tubular connector,

said plug being made of a thermosetting polyester synthetic resin having a compressive strength in excess of 20,000 psi. and a tensile strength in excess of 5,000 psi. and a flexural modulus of elasticity of the order of 600,000 pounds per square inch, and

a plurality of insulated electric wires disposed in said said wires being made of copper and insulated with a sheath of continuous polytetrafluoroethylene adhered thereto having a thickness of between .010 and .020 inch,

said sheath having a surface roughness of at least 50 microinches R.M.S.,

said wires being disposed with their lengths parallel to each other and the axis of the plug,

said wires being disposed in a uniform symmetrical spacing pattern, namely at the apices of adjacent equilateral triangles with a minimum separation between the outer peripheries of the sheaths at least equal to the outer diameter of the sheath,

said plug having end surfaces transverse to the axis thereof,

one of said end surfaces being at the end of the plug where said comically tapered exterior of the plug has its smallest diameter and being adapted to seat against a correlative surface at the bottom of said counterbore in said tubular connector,

another of said end surfaces being at the end of the plug where said conically tapered exterior of the plug has its largest diameter and being adapted to be engaged by a correlative surface of a jam nut screwed into the mouth of said counterbore,

said plug being molded with said wires in place forming an intimate bond between the plug and the insulation of the wires.

References Cited by the Examiner UNITED STATES PATENTS 2,447,489 8/48 Clark 174153 2,457,535 12/48 Diethert 174153 2,694,798 11/54 Cole 174-153 X 2,840,262 6/58 Learmonth et a1.

2,860,316 11/58 Watters et a1. 339-94 X 2,892,013 6/59 Gomberg 174-153 3,014,981 12/61 Appl 174-18 X E. JAMES SAX, Primary Examiner.

LARAMIE E. ASKIN, JOHN P. WlLDMAN,

Examiners. 

2. A SEAL COMPRISING A TUBULAR BODY HAVING CONNECTION MEANS AT EACH END, ONE END OF THE BODY HAVING A CONICAL COUNTERBORE WITH AND OUTWARDLY FLARING SEIZING TAPER AND AN ANNULAR OUTWARDLY FACING SHOULDER AROUND THE COUNTERBORE SPACED INWARDLY FROM SAID ONE END, A RESILIENT HIGH TEMPERATURE RESISTANT NON-ELECTRICALLY CONDUCTIVE, PLASTIC PLUG CONICALLY TAPERED CORRELATIVE TO SAID COUNTERBORE DISPOSED IN SAID COUNTERBORE IN ENGAGEMENT THEREWITH AND WITH SAID SHOULDER, A PLURALITY OF PLASTIC INSULATED COPPER WIRES EMBEDED IN SAID PLUG EXTENDING THERETHROUGH PARALLEL TO THE AXIS OF THE PLUG AND EACH SPACED LATERALLY FROM THE OTHERS, THE INSULATION ON SAID WIRES BEING ROUGHENED ON THE SURRFACE WHERE THE WIRES PASS THROUGH THE PLUG, SAID PLUG BEING MOLDED WITH SAID WIRES IN PLACE FORMING AN INIMATE BOND BETWEEN THE PLUG AND THE INSULATION OF THE WIRES. 